Your steering angle sensor probably just needs recalibration or is bad. Usually the simple reset is turn your steering wheel lock to lock (car on or off is okay). You've probably already done that without actually trying during the normal course of driving. I guess you can try again just to make sure. This simple reset is NOT the same as the recalibration. So, if they can't recalibrate then its obviously bad.

Since you mentioned your steering wheel is off-center a bit you would want to at least have your steering angle sensor recalibrated (if its not totally bad and doesn't need replacement). Recalibration is normally done at a dealer.

If it is bad, after replacement, its something that again would need to be recalibrated by the dealer (or a shop that has the capability). So ...

Best bet is take it to the dealer or an indy who has a GT1. The GT1 can help confirm diagnosis as it will give actual BMW specific codes. Also, once it finds the faults it will have the proper test plans to follow.

There might be a way to test whether you have a bad steering angle sensor without a GT1. I don't know how to do it but it probably involves reading resistance, etc with probes.

If you do a search on steering angle sensor, you might find something.